Neutralized phosphate esters of pentadecylphenol as corrosion inhibitors and preparation thereof



United States Patent NEUTRALHZED PHOSI HATE ESTERS 0F PENTA- DECYLPHENOL AS CORROSION INHIBITORS AND PREPARATION THEREOF Stanley H. Hesse, Bethlehem, and Joseph P. Copes,

Easton, Pa., assignors to General Aniline & Film Corporation, New York, N.Y., a corporation of Delaware N0 Drawing. Filed Sept. 12, 1962, Ser. No. 223,236

8 Claims. (Cl. 260-924) This invention relates to the preparation of new compositions of matter and relates more particularly to new and improved corrosion inhibiting compositions for use in preventing corrosion of metals, including iron, steel and ferrous alloys.

An important object of the present invention is to provide a new composition of matter useful as a corrosion inhibitor.

Another object of the present invention is the provision of new and improved corrosion inhibiting compositions which are effective in preventing or retarding metals from attack from a variety of corrosive agents such as water, brines, weak inorganic acids, organic acids, carbon dioxide, hydrogen sulfide, etc.

Still another object of the present invention is to provide corrosion inhibiting compositions which prevent corrosion of pipes or other equipment which is in contact with a corrosive-oil-containing medium.

A further object of the present invention is to provide a new and improved method of inhibiting corrosion.

Other objects and advantages of the present invention will be obvious from the following description.

The surprising discoverey has been made that neutralized phosphate esters of pentadecylphenol are particularly effective as corrosion inhibitors.

The corrosion inhibiting composition of the present invention finds special utility in preventing corrosion of pipes or other equipment which is in contact with a corrosive oil-containing medium, as, for example, in oil wells producing corrosive oil or oil-brine mixtures, in refineries, and the like. The corrosion inhibiting composition of this invention may, however, be used in other systems or applications, e.g., imparting resistance to metals from attack from a variety of corrosive agents, such as water, brines, weak inorganic acids, organic acids, carbon dioxide, hydrogen sulfide, etc.

The corrosion inhibitors of the present invention can be synthesized by heating pentadecylphenol and polyphosphoric acid to 115 C. in the absence of a solvent. The thus formed synthesized mixture of phosphate esters may be neutralized with an alkali hydroxide, an alkaline earth hydroxide, or an organic base such as cyclohexylamine, an aliphatic amine, or an aromatic amine. Also, if desired, the neutralized mixture of compounds of the present invention may be rendered anhydrous, e.g., by heating the mixture in a steam bath under vacuum.

When preparing the phosphate esters of the present invention, under the conditions described above, a mixture of compounds is formed and this mixture is an excellent corrosion inhibitor for metals.

The neutralized mixture of phosphate esters of the present invention is an economical and eflicient corrosion inhibitor, i.e., to inhibit rust formation in aqueous solutions, when formulated in petroleum-derived hydrocarbons such as lubricating oils, or when formulated in mixtures of methanol and water. Solutions containing from 0.5% to 2.0% of neutralized phosphate esters of pentadecylphonol have been found to yield optimum results.

One of the most desirous and important properties the compounds of the present invention possess is their solubility in petroleum-derived hydrocarbons and the ease 3,254,141 Patented May 31, 1966 'ice with which they may be rendered soluble in water. The advantages of such a range of solubilities are obvious.

The corrosion inhibiting composition of the present invention may be dissolved in small amounts in a liquid corrosive medium, and is thus kept in contact with the metal surface to be protected. Alternatively, the corrosion inhibiting mixture may be applied to the metal surface to be protected, either by itself or as a solution in some carrier liquid. However, continuous application of the corrosive inhibitor in admixture with the corrosive solution is the preferred method of use.

The present invention finds particular utility in the protection of metal equipment of oil wells and systems through which water is continuously flowing. For the protection of oil well equipment the corrosion inhibitor composition of this invention is fed in a conventional manner down the annulus of the well between the casing and producing fluid in the well and is pumped or flowed from the well with these fluids, thus contacting the inner wall of the casing, the outer and inner wall of tubing, and the inner surface of all well head fittings, connections and flow lines handling the corrosive fluid.

The corrosion inhibitor composition of the present invention may be used in liquid or solid form. When it is used in liquid form it is conventionally fed into the well annulus by means of a motor driven chemical injector pump, or it may be dumped periodically (e.g., once every day or two), into the annulus by means of a so-called boll weevil device or similar arrangement. When the corrosion inhibitor composition is in solid form, it may be dropped into the well as a solid lump or stick, it may be blown in as a powder with gas, or it may be washed in with a small stream of the well fluids or other liquid.

One method used to determine the corrosion inhibiting properties of the compounds of the present invention is that described by Baker et al. in Industrial and Engineering Chemistry, volume 41, pages 137-144 (1949).

Another procedure used to test the corrosion inhibiting properties of the compounds of the present invention is as follows:

The corrosion inhibiting compound of this invention is added to either water, a low-boiling hydrocarbon, or a high-boiling hydrocarbon, and ferrous metal turnings as they are formed are allowed to fall into the mixture. Thereafter, the turnings are drained and exposed to a relative humidity at a temperature of about 55 C. for 6 or more days.

The turnings protected by the corrosion inhibiting compounds of the present invention failed to show any indication of rust formation under these severe rusting conditions, whereas ferrous turnings added to untreated liquids, i.e., water, a low-boiling hydrocarbon, or a highboiling hydrocarbon, which do not contain the corrosion inhibiting compounds of the present invention, rust almost immediately, e.g., within a few minutes to an our.

The advantageous nature of the compounds of the present invention as corrosion inhibitors will be shown in the following examples:

EXAMPLE 1 A method of preparing the corrosion inhibiting phosphate esters of the present invention is as follows:

144.3 grams (0.5 mole) of 3 pentadecylphenol is heated with 20.0 grams of polyphosphoric acid at a temperature of C. for 5 hours. The reaction mixture was then neutralized to a pH of 7.7 by the addition of 35.5 milliliters of 8.19 N potassium hydroxide. The

neutralized mixture was rendered anhydrous by heating same on a steam bath under vacuum until a vacuum of 13 mm. was maintained. A small amount of amorphous precipitate was removed by filtering through a medium porosity fritted glass Buchner funnel. The product thus obtained was soluble in Bayol 50 (light) mineral oil at a 30% concentration.

EXAMPLE 2 A 2% solution of the compound of Example 1 was made in an oil of the type used in the lubrication of the crank cases of internal combustion engines. The solution as well as an untreated oil, i.e., free from the anticorrosion composition, was subjected to the above-mentioned static drop test of Baker et a1. Rusting occurred within a few hours with the untreated oil, while the treated oil protected the steel for days.

EXAMPLE 3 A 2% solution and a 0.5% solution of the corrosion inhibiting compound of Example 1, the neutralized phosphate esters of pentadecylphenol, were made in a highboiling hydrocarbon (initial boiling point, 375 C.) and steel turnings as produced were allowed to fall into these solutions and also into an untreated portion of the hydrocarbon.

Results of test The turnings placed in the untreated hydrocarbon rusted within a few hours whereas the turnings that were placed in the treated high-boiling hydrocarbon, at both the 2% and 0.5% concentrations, showed no traces of rust until two weeks after the treatment, and then only small traces.

EXAMPLE 4 A 2% solution and a 0.5% solution of the corrosion inhibiting compound of Example 1 were made in a petroleum ether (boiling point, 90100 C.) and these solutions were treated in the manner of Example 3.

Results of test The turnings placed in the untreated petroleum ether rusted within a few hours whereas the turnings placed in the 2% treated petroleum ether solution showed no traces of rust for over 6 days, and the turnings placed in the 0.5% treated petroleum ether solution showed no traces of rust for over 4 days.

EXAMPLE 5 A 50:50 mixture of methanol and water was used to dissolve the corrosion inhibiting compound of Example 1 to make 2% and 0.5% solutions. These solutions were tested in the manner of Example 3.

Results of test The untreated turnings rusted within a few hours whereas the turnings placed in the 2% and 0.5 bath concentrations did not rust for over 6 days.

EXAMPLE 6 Another method of preparing the corrosion inhibiting phosphate esters of the present invention is as follows:

1,443 grams (5.0 moles) of 3-pentadecylphenol were heated with 200 grams of polyphosphoric acid at 115 C. for 5 hours. The reaction mixture was then neutralized to a pH of 7.1 by the addition of 300 milliliters of 40% aqueous potassium hydroxide. The neutralized mixture was rendered anhydrous by heating the same on a steam bath at 95 C. under vacuum for 30 minutes after all foaming of the reaction mixture had ceased. The anhydrous material was filtered at 95-100 C. through a medium porosity, fritted glass Buchner funnel to yield 91% of the product.

EXAMPLE 7 A 2% and a 0.5% solution of the compound of Example 6 were made in petroleum ether (boiling point 90- 100 C.) and these solutions were tested in the manner v of Example 3. The turnings placed in the untreated petroleum ether rusted within a few hours, whereas no rusting was found on the turnings for over 6 days at both the 2% and 0.5% concentrations. The same results were obtained when 2% and 0.5% solutions were made in a high-boiling hydrocarbon.

When a 2% solution was prepared in lubricating oil and tested in the manner of Example 2, the treated oil protected the steel for days.

EXAMPLE 8 A method of making an analogous compound similar to that made in Examples 1 and 6 is as follows:

104.9 grams (0.2 mole) of the reaction product of 3- pentadecylphenol with 5 moles of ethylene. oxide was heated at 115 C. for 5 hours with polyphosphoric acid. The reaction mixture was neutralized to a pH of 7.7 by the addition of 11.3 milliliters 8.19 N potassium hydroxide and the same was rendered anhydrous by heating under a vacuum. The filtered material thus obtained was a clear, deep amber viscous liquid.

EXAMPLE 9 2% and 0.5% solutions of the compound of Example 8 were made in petroleum ether (boiling point 100 C.) and these solutions were tested in the manner of Example 3. Rusting occurred on the turnings placed into the treated solutions in less than a day. The same results were obtained on the turnings when 2% and 0.5% solutions were added to a high-boiling hydrocarbon.

EXAMPLE 10 When 117 grams (0.17 mole) of the acidic reaction mixture of Example 6 was neutralized to a pH of 9.15 with 40.7 grams of Armeen C and thereafter made anhydrous by heating under vacuum, the Armeen C salt of the phosphate esters of pentadeeylphenol was obtained.

Armeen C is a product which comprises approximately 8% octylamine, 9% decylamine, 47% dodecylamine, 18% tetradecylamine, 8% hexadecylamine, 5% octadecylamine, and 5% octadecenylamine.

EXAMPLE 11 2% and 0.5% solutions of the compound of Example 10 were made in petroleum ether (boiling point 90100 C.) and these solutions were tested in the manner of Example 3. After 1-2 days there was rusting of the chips treated by the 2% solution and protection from rusting Was afforded for less than a day by the 0.5% solution. The same results were obtained in a treated high-boiling hydrocarbon solvent, However, when a 0.5% solution of the compound was made in lubricating oil and tested in the manner set forth in Example 2, the treated oil protected the steel from rusting for days.

EXAMPLE 12 This is an example of a compound related to the corrosion inhibitor of the present invention, but not effective. 4 kilograms (6.5 moles) of the reaction product of nonylphenol with 9 moles of ethylene oxide Was heated at C. for 5 hours with 260 grams of polyphosphoric acid. The reaction mixture was neutralized to a pH of 7.0 by the addition of 435 milliliters of 40% aqueous solution of sodium hydroxide and then rendered anhydrous by heating under vacuum. The neutral product was heated to 120130 C. and filtered by gravity through paper upported in a stream-jacketed funnel to give a 97% yield of clear product.

EXAMPLE 13 2% and 0.5% solutions of the compound of Example 12 were made in water and these treated solutions were tested in the manner of Example 3. Less than a days protection against rusting was imparted to the steel turnings from both concentrations, The compound of Example 12 was insoluble in petroleum ether and also inscription is given merely by way of illustration and that variations may be made therein without departing from the spirit of this invention.

What is claimed is:

1. A neutral salt selected from the group consisting of cyclohexylamine, alkylamines, alkali metal salts and alkaline earth metal salts of phosphate esters of 3-pentadecylphenol and polyphosphoric acid.

2. Alkali hydroxide-neutralized phosphate esters of 3- pentadecylphenol and polyphosphoric acid.

3. C alkyl amine-neutralized phosphate esters of 3- pentadecylphenol and polyphosphoric acid.

4. Cyclohexylamine-neutralized phosphate esters of 3- pentadecylphenol and polyphosphoric acid.

5, A method of preparing corrosion inhibiting salts of phosphate esters of pentadecylphenol, comprising heating 3-pentadecylphenol with polyphosphoric acid to form a mixture of phosphate esters, in the absence of a solvent, at a temperature of about 115 C. for about 5 hours, neutralizing the reaction mixture of a pH of about 7 to 7.7 by the addition of a member selected from the group consisting of alkali hydroxide, cyclohexylamine, and an alkyl amine having from about 8 to about 18 carbon atoms.

6. A method of preparing corrosion inhibiting salts of phosphate esters of pentadecylphenol comprising heating 3-pentadecylphenol with polyphosphoric acid to form a mixture of phosphate esters at a temperature of about 115 C. for about 5 hours, neutralizing the reaction mixture to a pH of about 7.7 by the addition of about 8 N potassium hydroxide, thereafter rendering the neutralized mixture anhydrous by heating under vacuum, then filtering, whereby there is obtained a product which is soluble in petroleum-derived hydrocarbons and water.

7. A method of preparing corrosion inhibiting salts of phosphate esters of pentadecylphenol comprising heating 3-pentadecylphenol with polyphosphoric acid to form a mixture of phosphate esters at a temperature of about 115 C. for about 5 hours, neutralizing the reaction mixture by the addition of aqueous potassium hydroxide, thereafter rendering the neutralized mixture anhydrous by heating under vacuum, then filtering, whereby there is obtained a product which is soluble in petroleum-derived hydrocarbons and water.

8. A method of preparing corrosion inhibiting salts of phosphate esters of pentadecylphenol comprising heating 3-pentadecylphenol with polyphosphoric acid to form a mixture of phosphate esters at a temperature of about C. for about 5 hours, neutralizing the reaction mixture to a pH of about 7 to 7.7 by the addition of cyclohexylamine, thereafter rendering the neutralized mixture anhydrous by heating under vacuum, then filtering, whereby there is obtained a product which is soluble in petroleum-derived hydrocarbons and water.

Fierce et al. 260-46l CHARLES B. PARKER, Primary Examiner.

J. FREEWALD, H. B. GUYNN, DELBERT R. PHIL- LIPS, Assistant Examiners. 

1. A NEUTRAL SALT SELECTED FROM THE GROUP CONSISTING OF CYCLOHEXYLAMINE, ALKYLAMINES, ALKALI METAL SALTS AND ALKALINE EARTH METAL SALTS OF PHOSPHATE ESTERS OF 3-PENTADECYLPHENOL AND POLYPHOSPHORIC ACID. 